In Our View: Mount Hood Mysteries

Study seeks to gauge when and how volcano to the south will erupt

Published: February 23, 2014, 6:00 AM

Although it is one of the dominant features of the local landscape, residents still have much to learn about Mount Hood. You know, like when will it erupt again, and how will it erupt?Well, the answers to those questions cannot be assessed with certainty, but a new study does provide some fascinating insight. As detailed in a recent article by reporter Tom Vogt of The Columbian, a study co-authored by geologist Adam Kent of Oregon State University suggests that a pool of cooled magma lies 4 or 5 kilometers beneath the mountain.

"It's relatively cold for magma: 700 to 750 degrees Celsius," Kent told Vogt. "When magma is that cold, it's hard to make it move." Well, if you consider about 1,300 degrees Fahrenheit to be cold, then we suppose that's true. But such is the nature of volcanoes, which have held an endless fascination for locals since the cataclysmic 1980 eruption of Mount St. Helens.

Since then, part of the identity of this region of the country has been our link to volcanoes. And, you know, we're OK with that. But while Mount St. Helens has been much studied and much reported on — the mountain resumed spewing steam for a time in 2004 — Mount Hood remains a bit of a volcanic mystery. A 1980 study by the U.S. Geological Service determined that the "most likely eruptive event in the future will be the formation of another dome, probably within the present south-facing crater. The principal hazards . . . include pyroclastic flows and mudflows moving from the upper slopes of the volcano down to the floors of valleys. Ash clouds which accompany pyroclastic flows may deposit as much as a meter of fine ash close to their source."

Ah, ash. As anybody who lived in these parts at the time can attest, ash was the primary fallout — literally — of the Mount St. Helens eruption. But, as the study from Kent and co-author Kari Cooper of the University of California-Davis, determined, a Mount Hood eruption would be much different from the one that is part of local lore. For one thing, Mount Hood wouldn't have the internal buildup of pressure that resulted in an epic explosion on Mount St. Helens.

Yet the fact is that, at some point, Mount Hood will awake from dormant state. "What we found was that the magma has been stored beneath Mount Hood for at least 20,000 years — and probably more like 100,000 years," Kent said. "And during the time it's been there, it's been in cold storage — like the peanut butter in the fridge — a minimum of 88 percent of the time, and likely more than 99 percent of the time."

Geologists say that Mount Hood had an eruptive period between 12,000 and 15,000 years ago, between 1,500 and 1,800 years ago, and again from 200-300 years ago. It's a matter of time before the magma warms enough to start moving again.

Kent said an eruption would be similar to "what happens when you squeeze a tube of toothpaste in the middle. A big glob kind of plops out the top, but in the case of Mount Hood, it doesn't blow the mountain to pieces."

Given the destruction witnessed when Mount St. Helens blew its top — as well as the ecological and human cost — we would just as soon not see another mountain blown to pieces. Yet any activity would again make this region the center of the universe for geologists and those fascinated by the power of Mother Nature. There's no telling when that will happen; meanwhile, we'll be keeping on eye on the mountain to the southeast.